Board Feet of Lumber in a Log Calculator
Estimate how many board feet a log may yield using the three most common North American log scaling rules: Doyle, Scribner, and International 1/4-Inch. Enter the small end diameter, log length, quantity, and optional price per thousand board feet to calculate projected lumber volume and value.
Your Results
Enter your log dimensions and click calculate to see estimated board feet, volume, and value.
How to Use a Board Feet of Lumber in a Log Calculator
A board feet of lumber in a log calculator is designed to estimate the lumber volume contained in a round log before the log is sawn into boards. This type of estimate is essential for landowners, sawyers, foresters, timber buyers, portable sawmill operators, and woodworkers who want a practical way to compare log sizes, estimate product yield, or assign rough market value to standing or harvested timber. While no calculator can perfectly predict actual recovery from every log, a good log scale estimate gives you a standardized and widely accepted starting point.
In North America, log volume is commonly expressed in board feet. One board foot equals a piece of wood measuring 1 inch thick, 12 inches wide, and 12 inches long. That is 144 cubic inches of lumber. Logs are not rectangular, though, so the challenge is converting a tapered cylinder into an estimate of sawn lumber. That is where traditional log rules come in. A log rule is simply a mathematical method or table that estimates how many board feet of lumber can be sawn from a log of a given diameter and length.
This calculator uses the three best known log scaling rules: Doyle, Scribner, and International 1/4-Inch. Each rule makes different assumptions about slab loss, kerf, and taper, which is why the same physical log can have three different board foot estimates. Understanding those differences helps you compare apples to apples when negotiating stumpage, scaling delivered logs, or projecting sawmill output.
What Inputs Matter Most?
The most important inputs in a board feet of lumber in a log calculator are the small end diameter inside bark and the merchantable log length. Diameter is commonly measured at the small end because that dimension limits the maximum board width and affects waste. Length matters because longer logs generally yield more lumber, but longer pieces may also carry more sweep, taper, or defect. Quantity is included so you can estimate total yield for multiple logs of the same dimensions. An optional price per MBF, or price per thousand board feet, helps convert estimated volume into a rough gross value.
- Small end diameter inside bark: Usually the primary driver of board foot yield.
- Log length: Common lengths include 8, 10, 12, 14, and 16 feet.
- Number of logs: Useful for inventory, trucking, and mill planning.
- Scale rule: Determines how the estimate is calculated.
- Price per MBF: Helps translate volume into estimated revenue.
Board Foot Formula vs. Log Rule Formula
People often confuse a basic board foot formula for sawn lumber with a log scale formula. For boards, the classic board foot formula is straightforward:
Board Feet = (Thickness in inches × Width in inches × Length in feet) ÷ 12
Logs are different because you are estimating what can be recovered after cutting a round, tapered stem into rectangular lumber. The calculator above uses standard formulas commonly associated with the three log rules:
- Doyle: ((D – 4)² × L) ÷ 16
- Scribner: ((0.79 × D²) – (2 × D) – 4) × (L ÷ 16)
- International 1/4-Inch: ((0.199 × D²) – (0.642 × D) – 1.0) × L
In those formulas, D is the small end diameter inside bark in inches and L is the log length in feet. The formulas are most useful within normal sawlog ranges and are still estimates. Real recovery depends on sawing pattern, species, defects, kerf width, taper, crook, end checks, rot, and target product dimensions.
Which Log Rule Should You Use?
The best answer depends on your local market and how logs are bought and sold in your area. Some mills and buyers are deeply committed to a specific rule, and regional practice matters. A calculator is most helpful when it lets you compare rules side by side so you can understand the spread in estimated volume.
- Use Doyle if your local timber market traditionally scales logs that way. It tends to understate smaller logs and becomes more favorable as diameters increase.
- Use Scribner when dealing with regions or mills that still rely on Scribner Decimal C scaling.
- Use International 1/4-Inch when you want a more technically balanced estimate that accounts better for taper and kerf assumptions across a broader size range.
As a practical matter, a portable sawmill owner may use the calculator to compare expected volume across all three rules, then compare those estimates with actual lumber stacked after milling. Over time, that gives a better sense of how a specific operation, species mix, and sawing setup align with the published scale rules.
Comparison Table: Sample Board Foot Estimates by Log Rule
The table below shows example estimates for common log sizes using the standard formulas implemented in this calculator. These values illustrate how strongly the selected scale rule can affect the answer.
| Small End Diameter | Length | Doyle Estimate | Scribner Estimate | International 1/4-Inch Estimate |
|---|---|---|---|---|
| 12 in | 16 ft | 64 bd ft | 86 bd ft | 120 bd ft |
| 16 in | 16 ft | 144 bd ft | 166 bd ft | 243 bd ft |
| 18 in | 16 ft | 196 bd ft | 216 bd ft | 293 bd ft |
| 20 in | 12 ft | 192 bd ft | 219 bd ft | 348 bd ft |
| 24 in | 16 ft | 400 bd ft | 403 bd ft | 556 bd ft |
Notice that the spread between rules is not constant. On a 12 inch by 16 foot log, Doyle is much lower than International 1/4-Inch. As diameter increases, Doyle catches up somewhat, but the difference can still be significant. This is exactly why a board feet of lumber in a log calculator is useful: two people can discuss the same log and still arrive at different values if they do not agree on the scale rule first.
How Board Foot Estimates Affect Log Value
Once you know the estimated board feet, you can multiply total volume by a stumpage or delivered log price expressed in MBF. For example, if a load is estimated at 4,500 board feet and the market price is $650 per MBF, the rough gross value would be 4.5 × $650 = $2,925. This is not a final settlement number because grade, species, trucking, harvest cost, and scaling deductions all matter, but it is an excellent planning figure.
For individual logs, the value can vary widely. A straight, sound black walnut log may be worth far more per board foot than a similar sized low grade red oak log. Defects can also radically change actual yield. Hollow centers, severe sweep, insect damage, metal contamination, and decay all reduce what can be sawn into usable boards. That means a log calculator should be treated as an estimating tool, not a guarantee.
Comparison Table: Simple Lumber Equivalents in Board Feet
It is also helpful to connect log scale estimates with actual sawn lumber quantities. The table below shows how common board dimensions translate into board feet. This helps you visualize what a scaled log volume may represent in finished lumber terms.
| Lumber Piece | Board Foot Calculation | Board Feet per Piece | Pieces per 100 Board Feet |
|---|---|---|---|
| 1 × 6 × 8 | (1 × 6 × 8) ÷ 12 | 4 bd ft | 25 pieces |
| 2 × 4 × 8 | (2 × 4 × 8) ÷ 12 | 5.33 bd ft | 18.75 pieces |
| 2 × 6 × 10 | (2 × 6 × 10) ÷ 12 | 10 bd ft | 10 pieces |
| 1 × 12 × 12 | (1 × 12 × 12) ÷ 12 | 12 bd ft | 8.33 pieces |
| 3 × 8 × 10 | (3 × 8 × 10) ÷ 12 | 20 bd ft | 5 pieces |
Common Reasons Actual Lumber Yield Differs from Calculator Estimates
No matter how refined the formula is, actual sawmill recovery can deviate from scaled board feet. This is normal. Log rules simplify the real world so people can communicate volume consistently. The main sources of variation include species, taper, defects, sawing pattern, and equipment. Wide kerf circular mills often recover less than thin kerf band mills from the same log. Crooked logs produce more waste. Premium hardwood logs may be sawn for grade and width, while utility logs may be broken down more aggressively for pallets or cants.
- Kerf loss: Every saw cut turns some wood into sawdust.
- Slab loss: The curved outside of the log must be removed.
- Taper: Logs get smaller toward the top, reducing usable rectangular volume.
- Defects: Rot, checks, knots, shake, and crook reduce usable lumber.
- Trim and edging: Boards are often trimmed for clean ends and square edges.
- Target product mix: Cutting for grade can lower or raise yield compared with cutting for dimension stock.
Best Practices for Measuring Logs Accurately
A calculator is only as good as the measurements entered into it. Always measure diameter carefully and consistently. If you are using a log scale accepted by a buyer, use the same measurement rules that buyer uses. Some scales require diameter rounding conventions or specific handling of odd lengths. Bark thickness can matter a lot, especially in species with heavy bark, so many professional scaling systems rely on inside bark diameter rather than outside bark diameter.
- Measure the small end diameter as accurately as possible.
- Use inside bark measurements when your market standard calls for it.
- Measure merchantable length, not total crooked or defective length.
- Separate logs by species and grade whenever pricing differs.
- Use the same log rule consistently for all comparisons.
When a Calculator Is Especially Useful
A board feet of lumber in a log calculator is valuable in several real world situations. A woodland owner can estimate the amount of saleable timber before requesting bids. A custom sawyer can quote milling jobs more intelligently. A woodworker buying logs from a tree service can estimate whether the material is worth hauling and milling. A farm owner clearing fencerows can compare the value of sawlogs versus firewood. Even experienced foresters benefit from a fast calculator because it speeds up what would otherwise be repetitive hand calculations.
Limitations You Should Keep in Mind
Even an excellent calculator is not a substitute for a professional timber cruise, a formal scale ticket, or a sawmill tally. It also does not address grade. Two logs with identical dimensions can differ tremendously in value if one produces clear lumber and the other produces low grade boards. Likewise, a highly figured specialty hardwood may have niche value well above commodity scale prices. Use the calculator for planning, screening, and communication, but do not treat the result as a final settlement number without considering species, grade, market conditions, and defects.
Authoritative Forestry and Wood Measurement Resources
Final Thoughts
The most effective way to use a board feet of lumber in a log calculator is to treat it as a decision support tool. Enter accurate dimensions, compare multiple scaling rules, and remember that the final amount of usable lumber depends on both the log and the milling process. If your goal is budgeting, valuation, or comparing offers, the calculator gives you a strong baseline. If your goal is exact yield, pair the estimate with real world sawing records and regional scaling standards. Over time, that combination of field measurement and actual production data will give you the most reliable picture of what your logs are truly worth.